gianfar: Fix skb allocation strategy

gianfar was unable to handle failed skb allocation for rx buffers, so
we were spinning until it succeeded.  Actually, it was worse--we were
spinning for a long time, and then silently failing.  Instead, we take
Stephen Hemminger's suggestion to try the allocation earlier, and drop the
packet if it failed.

We also make a couple of tweaks to how buffer descriptors are set up.

Signed-off-by: Andy Fleming <afleming@freescale.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

diff --git a/drivers/net/gianfar.c b/drivers/net/gianfar.c
index b917616..99a4b99 100644 (file)
--- a/drivers/net/gianfar.c
+++ b/drivers/net/gianfar.c
@@ -98,7 +98,6 @@
 #include "gianfar_mii.h"
 
 #define TX_TIMEOUT      (1*HZ)
-#define SKB_ALLOC_TIMEOUT 1000000
 #undef BRIEF_GFAR_ERRORS
 #undef VERBOSE_GFAR_ERRORS
 
@@ -115,7 +114,9 @@ static int gfar_enet_open(struct net_device *dev);
 static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev);
 static void gfar_timeout(struct net_device *dev);
 static int gfar_close(struct net_device *dev);
-struct sk_buff *gfar_new_skb(struct net_device *dev, struct rxbd8 *bdp);
+struct sk_buff *gfar_new_skb(struct net_device *dev);
+static void gfar_new_rxbdp(struct net_device *dev, struct rxbd8 *bdp,
+               struct sk_buff *skb);
 static int gfar_set_mac_address(struct net_device *dev);
 static int gfar_change_mtu(struct net_device *dev, int new_mtu);
 static irqreturn_t gfar_error(int irq, void *dev_id);
@@ -783,14 +784,21 @@ int startup_gfar(struct net_device *dev)
 
        rxbdp = priv->rx_bd_base;
        for (i = 0; i < priv->rx_ring_size; i++) {
-               struct sk_buff *skb = NULL;
+               struct sk_buff *skb;
 
-               rxbdp->status = 0;
+               skb = gfar_new_skb(dev);
 
-               skb = gfar_new_skb(dev, rxbdp);
+               if (!skb) {
+                       printk(KERN_ERR "%s: Can't allocate RX buffers\n",
+                                       dev->name);
+
+                       goto err_rxalloc_fail;
+               }
 
                priv->rx_skbuff[i] = skb;
 
+               gfar_new_rxbdp(dev, rxbdp, skb);
+
                rxbdp++;
        }
 
@@ -916,6 +924,7 @@ rx_irq_fail:
 tx_irq_fail:
        free_irq(priv->interruptError, dev);
 err_irq_fail:
+err_rxalloc_fail:      
 rx_skb_fail:
        free_skb_resources(priv);
 tx_skb_fail:
@@ -1328,18 +1337,37 @@ static irqreturn_t gfar_transmit(int irq, void *dev_id)
        return IRQ_HANDLED;
 }
 
-struct sk_buff * gfar_new_skb(struct net_device *dev, struct rxbd8 *bdp)
+static void gfar_new_rxbdp(struct net_device *dev, struct rxbd8 *bdp,
+               struct sk_buff *skb)
+{
+       struct gfar_private *priv = netdev_priv(dev);
+       u32 * status_len = (u32 *)bdp;
+       u16 flags;
+
+       bdp->bufPtr = dma_map_single(&dev->dev, skb->data,
+                       priv->rx_buffer_size, DMA_FROM_DEVICE);
+
+       flags = RXBD_EMPTY | RXBD_INTERRUPT;
+
+       if (bdp == priv->rx_bd_base + priv->rx_ring_size - 1)
+               flags |= RXBD_WRAP;
+
+       eieio();
+
+       *status_len = (u32)flags << 16;
+}
+
+
+struct sk_buff * gfar_new_skb(struct net_device *dev)
 {
        unsigned int alignamount;
        struct gfar_private *priv = netdev_priv(dev);
        struct sk_buff *skb = NULL;
-       unsigned int timeout = SKB_ALLOC_TIMEOUT;
 
        /* We have to allocate the skb, so keep trying till we succeed */
-       while ((!skb) && timeout--)
-               skb = dev_alloc_skb(priv->rx_buffer_size + RXBUF_ALIGNMENT);
+       skb = netdev_alloc_skb(dev, priv->rx_buffer_size + RXBUF_ALIGNMENT);
 
-       if (NULL == skb)
+       if (!skb)
                return NULL;
 
        alignamount = RXBUF_ALIGNMENT -
@@ -1350,15 +1378,6 @@ struct sk_buff * gfar_new_skb(struct net_device *dev, struct rxbd8 *bdp)
         */
        skb_reserve(skb, alignamount);
 
-       bdp->bufPtr = dma_map_single(&dev->dev, skb->data,
-                       priv->rx_buffer_size, DMA_FROM_DEVICE);
-
-       bdp->length = 0;
-
-       /* Mark the buffer empty */
-       eieio();
-       bdp->status |= (RXBD_EMPTY | RXBD_INTERRUPT);
-
        return skb;
 }
 
@@ -1544,10 +1563,31 @@ int gfar_clean_rx_ring(struct net_device *dev, int rx_work_limit)
        bdp = priv->cur_rx;
 
        while (!((bdp->status & RXBD_EMPTY) || (--rx_work_limit < 0))) {
+               struct sk_buff *newskb;
                rmb();
+
+               /* Add another skb for the future */
+               newskb = gfar_new_skb(dev);
+
                skb = priv->rx_skbuff[priv->skb_currx];
 
-               if ((bdp->status & RXBD_LAST) && !(bdp->status & RXBD_ERR)) {
+               /* We drop the frame if we failed to allocate a new buffer */
+               if (unlikely(!newskb || !(bdp->status & RXBD_LAST) ||
+                                bdp->status & RXBD_ERR)) {
+                       count_errors(bdp->status, dev);
+
+                       if (unlikely(!newskb))
+                               newskb = skb;
+
+                       if (skb) {
+                               dma_unmap_single(&priv->dev->dev,
+                                               bdp->bufPtr,
+                                               priv->rx_buffer_size,
+                                               DMA_FROM_DEVICE);
+
+                               dev_kfree_skb_any(skb);
+                       }
+               } else {
                        /* Increment the number of packets */
                        dev->stats.rx_packets++;
                        howmany++;
@@ -1558,23 +1598,14 @@ int gfar_clean_rx_ring(struct net_device *dev, int rx_work_limit)
                        gfar_process_frame(dev, skb, pkt_len);
 
                        dev->stats.rx_bytes += pkt_len;
-               } else {
-                       count_errors(bdp->status, dev);
-
-                       if (skb)
-                               dev_kfree_skb_any(skb);
-
-                       priv->rx_skbuff[priv->skb_currx] = NULL;
                }
 
                dev->last_rx = jiffies;
 
-               /* Clear the status flags for this buffer */
-               bdp->status &= ~RXBD_STATS;
+               priv->rx_skbuff[priv->skb_currx] = newskb;
 
-               /* Add another skb for the future */
-               skb = gfar_new_skb(dev, bdp);
-               priv->rx_skbuff[priv->skb_currx] = skb;
+               /* Setup the new bdp */
+               gfar_new_rxbdp(dev, bdp, newskb);
 
                /* Update to the next pointer */
                if (bdp->status & RXBD_WRAP)
@@ -1584,9 +1615,8 @@ int gfar_clean_rx_ring(struct net_device *dev, int rx_work_limit)
 
                /* update to point at the next skb */
                priv->skb_currx =
-                   (priv->skb_currx +
-                    1) & RX_RING_MOD_MASK(priv->rx_ring_size);
-
+                   (priv->skb_currx + 1) &
+                   RX_RING_MOD_MASK(priv->rx_ring_size);
        }
 
        /* Update the current rxbd pointer to be the next one */